Yukon Gear Trac Loc Positraction / Ford Super 8.8in / 34 Spline / 15-20 F-150
Owners of 2015-and-newer Ford F-150s with the Super 8.8 rear axle usually land here for one of two reasons: an open rear that leaves one tire spinning on wet grass, gravel or a boat ramp, or a worn factory limited slip that no longer pulls both tires. The Yukon Trac Loc YC F8.8-4-34T/L is a complete loaded carrier for that axle, with a clutch-type limited slip built for 34-spline axle shafts. It is aimed at daily-driven trucks and mild off-road use, where you want both tires working without the noise and harshness of a locker.
The Super 8.8 is the 8.8 inch rear Ford put under the aluminum-body F-150 starting in 2015, with larger 34-spline shafts than the older 28 and 31-spline 8.8. Inside the Trac Loc, clutch packs sit behind each side gear and are preloaded by a spring. In a normal turn the outer tire overrides the clutches and the truck drives like an open axle. When one tire starts to slip, the clutches resist the speed difference and push more torque to the tire with grip. Yukon describes it as a less aggressive, street-friendly unit, which is the right fit for a truck that tows and commutes more than it crawls.
Make sure the truck has the Super 8.8 and not the 9.75 inch rear, which Ford also used in these F-150s. The axle tag and the axle code on the door label tell you which one and the ratio; our Ford 8.8 vs 9.75 comparison shows how to tell them apart under the truck. If the complaint is chatter in turns rather than one-tire spin, try the fluid fix in our 8.8 Traction-Lok chatter guide before replacing the carrier. On a 4x4 truck, remember the front axle is a separate 8.8 IFS unit; the Eaton Truetrac for the 2009-2023 F-150 4x4 front 8.8 is the matching front upgrade.
Our listing title says 2015-2020 F-150. Yukon's current fitment for this carrier is wider: the 2015-2024 F-150 with the Super 8.8 rear and the 2025-2026 F-150, all with 34-spline shafts. Yukon specifies 3.31 and numerically higher ring and pinion ratios, so confirm your ratio before ordering. This part is not for the older 28 or 31-spline 8.8, the Super 8.8 in the 2015-up Mustang, which Yukon sells as a separate part, or the 9.75 rear. Match the axle and spline count, or send us your year and VIN and we will check it. More axle parts are in our hard parts category.
Removing the carrier means pulling the axle shafts, then the carrier caps and the old case. Use new carrier bearings when you move the ring gear over; the Super 8.8 rear master bearing kit covers bearings and seals, and a side bearing puller set gets the old bearings off without damage. If you are changing ratio at the same time, the Yukon 3.73 gear set for the 2015-up F-150 8.8 sits inside this carrier's 3.31-and-up range. Torque the ring gear bolts with thread locker and re-check backlash: Yukon's chart lists 0.006-0.011 inch for a five-cut gear set and 0.008-0.012 inch for two-cut gears on the 8.8 Super. Because this is a clutch-type unit, fill with gear oil suited to limited slips and add friction modifier as needed (see our fluids category); our friction modifier guide explains how much. Drive gently through some figure eights for the first few miles to let the clutches seat.
| Brand | Yukon Gear & Axle |
| Part number | YC F8.8-4-34T/L |
| Fits | Yukon Gear Trac Loc Positraction / Ford Super 8.8in / 34 Spline / 15-20 F-150 |
| Type | Differential Housings |
| Condition | New |
| Ships | Same business day (in stock), from the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. This carrier is for the 2015-up Super 8.8 with 34-spline shafts. Earlier F-150s with the 8.8 use 28 or 31-spline shafts and a different carrier.
No. The 9.75 is a different axle with its own carrier. Check the axle tag or door label code to confirm which rear you have.
Yukon lists this carrier for 3.31 and numerically higher ratios. If your truck has a lower numerical ratio, send us the axle code so we can confirm fit before you order.
Yes. The Trac Loc uses clutch packs, so run a gear oil that already contains friction modifier or add it. Too little causes chatter in tight turns.
No. It is a clutch-type limited slip that biases torque to the tire with grip while still letting the wheels differentiate in turns. For a full locker on the Super 8.8, ask us about locker options for your build.
